A handbag or a tote is a must when traveling. A handbag as your second carry on item on the plane or you can pack a foldable nylon tote. The handles of the purse should cradle comfortably under your arm and large enough to hold everything you need for the day while away from your hotel.
I would not bring your most expensive purse. You do not want to risk it getting lost or stolen; in addition it will add wear and tear. Your purse will be on the floors of train stations, restaurants, park benches etc. so it needs to be durable, not delicate.
You can pick a dark neutral or you can pick a color that complements your scarves or other accessories. European women do tend to carry colored handbags so color is not out of the question.
Many a chic French woman carries a nylon Longchamp bag. These bags consist of nylon and fold up into their own little case, voila a great travel tote. These bags can be pricey but luckily I have seen a few copycat bags at department stores with the same feature. A foldable tote is a good option if you donâ€™t want to deal with carrying your backpack and a purse at the same time, which can be a trick.
What I usually carry in my purse is my camera, umbrella and/or rain hat, Purell (donâ€™t leave home without it), maps, guidebook or torn out pages, blister kit, tissues(helpful when thereâ€™s no toilet paper), sunglasses, journal, and makeup. The one thing you shouldnâ€™t keep in your purse is money, or at least all of your money. I usually put in what Iâ€™ll need for my immediate activities, coffee, metro, museum and then move my money from my money belt to my purse when Iâ€™m in a bathroom or some other not too public place.